Suction drum strainer



Sept- 2l, 1954 P. G. H. OHLSTRM 2,689,654

SUCTION DRUM STRAINER Filed Jan. 3l 1951 2 Sheets-Sheet l INVENTOR. Paul Gusav Henr/ lsrm ATTORNEK P. G. H. OHLSTRM SUCTION DRUM STRAINER Sept. `21, 1954 2 sheds-sheet 2 Filed Jax-1. 31, 1951 INVEN TOR.

Paul Gusav Hnr/K Ola/#fam W2K @wir A T TURA/EV.l

V againstoutside air;

Patented Sept. 2l, 1954 t UNIT llifk STATES PAT @FFI 2,689,654

SUTION DRUMSTRAINER Raul Gustav-Henrik.0hlstrnn,Karhula, Finlands Application `lanuary 31, 1951*, Serial No; 208;'715.

(Cl. 2do-2.011)

5 Glaims;

Ron eliminating the drawbacks of hi'ghproduction. costs `and;maintenance dicultiestypical' at. dmanstrainers provided! withn internal socalled vanuum segmentsftightlyitted against-the drumuintenior; ithaslbeen the: drum: with. a delivery. compartment located; om the outer surface: of the drum and packedi Ati theI delivery.` section the. delivery compartment. follows the Vstrainer sur inne the-who1e breadth; thereof and1 over' agreateror: shorter peripheral l'ength4 thereof; ain-tightly. packedi against the sameandagainst mide air at: bothy ends: thereof; These pack-- ings, whioinare oir prioiz'lenown construction as is= the delivery compartment;A itself; consist of drag-v ging packings oripreferablyl of. a shaped delivery miler: in combinationwith dragging packingsA or addioionitllyj one or.- more rollers co-operatingl with.; each' other and with. the straining drum: It hasu also been proposed that'` the delivery'compianterreno.irritaentirety.` consister? a spacelimited onzcme. side by thestmainersurface; on the other side by; two reciprooally.I operating rollers`V arfranged. press` against each other. V'I'he roller' located highest'. up: and; arranged yi'eldablyf against the.` peripheredi surface i oi? the strainer drum. serves a deliyerryfroller` and thus; Withinterposed? stock: layer;I maintains a tight nt against.-th'ef` 'Iheiother'roller locatedE lower on a. dragging packingacoz-operatingi therewith* (and for'. whicha third: roller' can besubstituted)` packs, the;v conipartnrlent` against. the drum as also against the first' mentioned roller and against the stock vat CNonwegianPatent'No. 65,691); In the latter apparatus. (Norwegian Patent No; 65;.6910 and. formenl apparatuses (feu g. Swedish Patent' No;A 76:,779` andi the-f Norwegian Patents suggested' to provide Noi. plr andlilo:l 65,851) the vacuum pipe is connected: respectlvelyftothe` strainer drum and' delivery compartment: for producing the desired* reduced. pressureiin the strainer drum. The object: is that the deliveryA compartment, whichY through thefopenings in the strainer surfacecomh muncates. with the drum interior, be thereby maintained at.` reduced' pressure equai to orA slightlyfgfreaterr than.` the: reducedpressure in the drum. The.- stock layer` built; up oir the peripheral surface.' oi the rotating. drumfollows therewith. and enters. into; the, delivery compartment past. the.: yieldable: packing thereofI .ti't'trxii againstY the dimm, wherebyl thef tight: ft'- against outsidei aix: is.. maintained. In. consequence of the reduced. pressure in the: delivery cornpairtment the stool; layer can now be continuously removed from. the strainer surface. either: by meansof the delivery; roller. mnntioning` simultaneously as packing elementor byfnieans-of ascraperon the-f twoin combination with eacii-` other, eitherl to be passedA through tlie2 twofrollers: as: a-continuous stockH sheet orf to drop` into and be carried` away* from the lower part of the delivery: compartment to a chamber impermeable ton outside air' andi under reducedpressure equai tof that in: the d'eliverycompartment; It isalso possible to with-` draw the strained pulp through a` drain trapf which preventsfthe entryoff air intoithe delivery means;

Asi compared tou thecelllprovidedi-drumstraineijs the above described drumsbr-ainers are simpleinsconstruotion; in addition to-.wliich the packing7 means-are accessible for inspection andi repair. However, it has turned! outV that` the drumi describedf has'7 no) practical utility because of unsatisfactory operation in respect. of stock' delivery ashas: been ascertained? in tests made in conjunction with the present inventionA It has: now been*A established. that-.ini the abovedescribed drum strainers the reduced pressure Within the delivery. compartment'A and the reduced? pressure: within: the strainer` drum are not equallygreat. but are peorlyf proportioned tox eacir athen. On: applying suction: through thestrai'nerl' drum theireduced; pressure within the drumf becomesa muciii too4 great; in proportion@ to: the: reduced` pressurein the delivery. compartment, in conseguenze of Whichfremovali ot'stocl" layer isl incomplete: and thea strainer" tends. to: clogr` up quickly; OnA applying;` suction through the delivery compartment the relationshiplfV betweenl reduced: pressuresA is. reversedf which! means: thatv the: eiicienny.A ot the: strainer becomes: materially! reduced;Y the: stock layerr on the: strainer surfacel wilh only be: incompietely: dewatered and' accumu' lates for: the: greater' part before the packing' means between drum. and: delivery.7 compartment*- withontentei'i; therein evendi the packing consist/sof: a deliveryiroller.

It has now surprisingly been; found' that-open ationai diiii'cul'ties` can be avoidedi when drun'i1 st-nainers. ot the kinii hereinabove described' areJ provicledi with means.: fon the continuous. adjust ment of the.` reduced! pnessure within. the strainer drinnY relative to; the: neduced pressure withini the delivery compartment communicating with the@ strainer. surface and limited:V by: the delivery means.

In adjusting; the reducedpressure within' thel stnai'ner.' drinn relative toythe `reduced pressurel ini the delivery' compartment' according tfotli'ef invention means: are provided for interconnectinge the-pressures ini the drunr and* in: the delivery compantm'ent. For producing the reduced pres"- sure desired either the strainer drum or the delivery compartment or the two can be connected with a vacuum source, either through respective separators or through a common suction pipe communicating with the respective compartments. The reduced pressure can also be produced by utilizing the falling motion of the extracted water on discharging it from the drum. The pressure 'connection between the strainer drum and the delivery compartment can also be provided with adjusting means so as to be regulatable.

Generally, the only requisite to the satisfactory delivery in accordance with the present invention is the equalization of reduced pressures within the strainer drum and the discharge compartment, which is simply achieved by using a pressure pipe to interconnect the respective compartments. In certain instances, however, it may be advantageous to maintain within the delivery compartment, either during the whole straining operation or only in running risks for unsatisfactory stock delivery a reduced pressure slightly greater than that in the strainer drum. y

Two embodiments of the invention are illustrated by way of example in the accompanying drawings, in which:

. Fig. 1 shows a vertical sectional view of a strainer embodying the present invention.

Fig. 2 is a horizontal sectional elevation of the end portion of the same, and

Figs. 3, 4 and 5 show sectional views of various means for carrying away the strained pulp from the strainer.

Fig. 6 shows a vertical sectional view of another strainer embodying the invention,

Fig. 'l is a horizontal sectional elevation of the end portion of the same, while Figs. 8 and 9 each show sectional views of two details of the delivery means.

In the drawing at I is indicated a strainer drum which rotates in the direction shown by the arrow. At 2 is indicated the strainer surface of the drum either of perforated plate or made of or provided with straining wire. At 3 is indicated a suction pipe from the straining drum to a vacuum source (not shown), at 4 a strainer vat into which the stock to be strained is introduced through the inlet 6 shaped as a drain trap 5. The extracted Water is discharged from the drum interior through openings in the respective end faces thereof, said openings having communicationwith the common outlet'l. With sufficient fall height also the falling movement of the water discharging through the outlet 1 can be utilized for producing reduced pressure in the straining drum.

Referring now to the construction shown in Figs. 1-5, the `drum is provided with a prior known delivery compartment 8 located on the outside of the drum and oppositely to the stock inlet 6, and extending downwardly to open into the stock outlet 9. The otherwise closed delivery compartment 8 communicates with the strainer surface and is tted tightly against the same partly by means of the dragging packing I0, partly by the roller II shaped as a delivery roller. At the respective end faces of the drum the delivery compartment is tightly fitted, by prior known end packings I2, against the drum periphery so as to be impermeable to outside air. The delivery roller II is in prior known manner turnably mounted at I3. The shiftable weights I arranged at the respective ends of the delivery roller axle I4 keep the roller resiliently bearing against the strainer drum surface. The weight-loaded spring IB arranged to engage the lower part of the dragging packing I0 serves to keep the packing I0 pressed against the strainer surface 2 especially at the outset of the straining operation, before the stock vat 4 is lled up with pulp. The stock layer I1 built up on the drum in rotary motion is removed by the delivery roller II, from which it falls down and is so carried away, by means indicated at I8, through the outlet 9 so that no outside air enters into the delivery compartment 8. Into the opening of the delivery compartment 8 communicating with the vstrainer surface and underneath the delivery roller II is advantageously arranged a roller I9 for receiving and dropping the stock from the delivery roller into the lower part of the delivery compartment 8. The roller ISI-can be driven at a slightly greater peripheral speed than that of the delivery roller II rotating with the drum so as to exert a certain pull on the stock sheet to be carried by the roller I9 and thereby to insure its removal from the delivery roller II. Underneath the roller I9 is arranged the scraper 20 which removes the stock particles possibly still travelling with the said roller and the shower pipe 2| is so arranged as to direct a strong spray of water against the strainer surface 2 to clean it. Through the pipe 22 dilution water in regulated amounts can be introduced when desired into the stock in the bottom part of the delivery compartment 8. The Weight loaded scraper 23 is arranged as a safety mea-sure, especially at the outset, to insure the complete removal of stock from the delivery roller. To provide continuous satisfactory delivery there is arranged at the respective drum end faces the pressure equalizer pipe 24 which interconnects the interiors of the straining drum I and the delivery compartment 8 so as to constantly equalize the reduced pressure in the two compartments-This pressure equalizing pipe can also be replaced by other means, e. g. means which connect the strainer drum and the delivery compartment to a suction pipe in common to both or to respective regulatable suction pipes.

Figs. 3, 4 and 5 show three diiferent embodiments for discharging the stock under vacuum from the delivery compartment 8.y According to Fig. 3, a construction is shown comprising a mixture feed pump arranged at the one end of a screw I8 for discharging the stock which in this case is diluted with water introduced through pipe 22. The abovementioned mixture pump overcomes the vacuum in the strainer. Therefore, if a plurality of strainers are placed one after another, as is the case in continuous sulte and sulfate pulp washing, all the strainers can be arranged on the same level or above each other and the stock can directly be pumped to the inlet side of the following strainer.

According to Fig. 4, the undiluted stock is fed by the screw I8 through an outlet constricted according to this embodiment and against which the stock is pressed, and therefore provides-sufficiently tight iit against the entrance of air.

According to Fig. 5 diluted stock is fed by the screw I8 through a drain trap which preventsair from entering into the delivery compartment.

In the strainer drum according to Figs. 6 and 7 the stock layer built up on the strainer surface is passed in the form of a continuous stock sheet between the delivery roller II and the roller 25 cooperating therewith, which latter is fitted with ing a packing element prior known packing elements so as to provide an air tight compartment on that side of the two rollers which points towards the strainer drum. According to the invention this delivery compartment communicates with the strainer drum interior for the equalization of reduced pressure and the vacuum is designed to be produced by the utilization of the falling movement of water discharging through the outlet 1. Naturally other measures can be resorted to in adjusting the relationship between the reduced pressure in the strainer drum and the reduced pressure in the delivery compartment and vacuum can also be produced by coupling the drum and/ or delivery'compartment to a vacuum source.

Eig. 8 shows how the delivery roller I I is turnably mounted and Fig. 9 shows the lower roller 25 with the dragging packing 26 set to bear thereon and also the shower pipe 2| and dragging packing l0 in larger scale.

It is to be understood that a plurality of constructional modifications can be made without deviating from the scope and spirit of the invention while mintaining the requisite that the reduced pressure in the strainer drum and the reduced pressure in the delivery compartment communicating with the strainer surface and limited by the delivery means can be adjusted or equalized. Naturally the delivery means and the delivery compartment can be formed so as to provide a unit detachably secured to the drum strainer or adjustable vertically.

I claim:

1. In suction drum strainer construction, a vat for receiving a suspension to be strained, a strainer drum mounted for rotation with a portion thereof within said vat, said drum having a substantially unobstructed interior, and being formed with a peripheral strainer surface, means for creating a suction in said drum and a delivery compartment mounted adjacent the periphery of said drum, said delivery compartment being formed with an opening therein in opposed relation with respect to said strainer surface of said drum for receiving the strained stock layer built up on said strainer surface, packing means for sealing the border of said opening against said strainer surface for preventing the entrance of outside air into said Vdelivery compartment and into said drum said packing means includsurface of said drum below said delivery compartment and extending into said vat for preventing the suspension in said vat from being drawn up into said delivery compartment whereby the reduced pressure created in said drum by said suction creating means is communicated to the interior of said delivery compartment through said strainer surface and through said opening, and an additional communicating element extending from said drum to said delivery compartment outside of said opening and communicating with the interior of said drum and said delivery compartment for assisting and equalizing the reduced pressures therein.

2. A construction as in claim 1 wherein said additional communicating element is a pipe and said pipe on one end thereof communicates with the interior of said drum, and on the other end thereof with the interior of said delivery compartment.

3. A construction as in claim 2 wherein adjusting means is provided in said pipe for adjusting the pressure between said drum and said delivery compartment.

engaged with the strainerV 4. In suction drum strainer construction, a vat for receiving a suspension to be strained., a strainer drum mounted for rotation with a portion thereof within said vat, said drum having a substantially unobstructed interior, and being formed with a peripheral strainer surface, a delivery compartment mounted adjacent the periphery of said drum, said delivery compartment being formed with an opening therein in opposed relation with respect to said strainer surface of said drum for receiving the strained stock layer built up on said strainer surface, packing means for sealing the border of said opening against said strainer surface for preventing' the entrance of outside air into said delivery compartment and into said drum said packing means including a dragging packing engaging the surface of said strainer drum below said delivery compartment, said dragging packing extending into said vat to prevent suspension in said vat from being drawn up into said delivery compartment, and a common suction pipe in communication with said drum and said delivery compartment whereby the suction in the interior of said drum and in the interior of said delivery compartment can be equalized.

5. In suction drum strainer construction, a vat for receiving a suspension to be strained, a strainer drum mounted for rotation with a portion thereof within said vat, said drum having a substantially unobstructed interior and being formed with a peripheral strainer surface, means for creating a suction in said drum, and a delivery compartment mounted adjacent the periphery of said drum, said delivery compartment being formed with an opening therein in opposed relation with respect to said strainer surface of said drum, a pair of rollers mounted in said delivery compartment adjacent said opening, one of said rollers being in engagement with said strained stock on` said strainer surface for delivering the same therefrom, and the other of said rollers being spaced from the first of said rollers, said spacing being sufficient for the passing of the strained stock therethrough and providing for the delivery of the same as a continuous sheet, packing means for sealing the border 0f said opening against said strainer surface for preventing the entrance of outside air intoV said delivery compartment and into said drum whereby the reduced pressure created in said drum by said suction creating means is communicated to the interior of said delivery compartment through said strainer surface and through said opening, and an additional communicating element extending from said drum to said delivery compartment outside of said opening and communieating with the interior of said drum and said delivery compartment for assisting and equalizing the reduced pressures therein.

References Cited in the iile of this patent UNITED STATES PATENTS Number Name Date 690,030 Parker Dec. 31, 1901 1,648,670 Atwell Nov. 8, 1927 1,914,742 Hillier June 20, 1933 2,131,303 Selund Sept. 27, 1938 FOREIGN PATENTS Number Country Date 57,153 Norway Oct. 12, 1936 65,691 Norway Jan. 18, 1943 65,851 Norway Mar. 1, 1943 76,779 Sweden Jan. 18, 1932 

